The present invention relates to a method for controlling a capstan phase during slow playback and a servo system for a video cassette recorder (VCR) adopting the same, and more particularly, to a method for controlling a capstan phase during slow playback and a servo system for a video cassette recorder (VCR) adopting the same in which a slow motion image can be clearly viewed without noise during slow playback in the VCR.
A servo system for use in a VCR includes a drum servo for controlling the rotational speed of a head to be constant and a capstan servo for controlling a track and maintaining a tape speed to be constant. The capstan servo controls the phase and speed of a capstan motor so that a head can accurately travel over a particular track, and maintains a tape speed to be constant according to a reproduction or recording mode.
A capstan speed control means controls rotation of a capstan motor by obtaining a capstan speed error voltage from a capstan frequency signal corresponding to a tape speed. During abnormal speed playback such as slow playback, a pause and a selective playback operation, a step slow control voltage output from a microcomputer is applied to a capstan speed control voltage.
During reproduction, a capstan phase controller controls a capstan motor by the procedure which compares the frequency of a control signal recorded on a control track of a tape with a reference frequency to thereby obtain a capstan phase error voltage, and adds the obtained capstan phase error voltage to a capstan speed control voltage.
However, the above conventional VCR controls a capstan speed by using a step slow method which makes a capstan motor repetitively rotate and stop during slow playback, with a result that an image is discontinuously displayed. For this reason, a slow motion image which can be seen from a general TV or movie cannot be provided. Also, since a control signal which becomes a reference during reproduction is irregularly read from a tape, the phase of a capstan motor cannot be controlled, and thereby produces noise on a screen.